Stars Trails over Armazones

Multiple-exposure picture taken looking west from the top of the 3060-metre-high Cerro Armazones, the selected site for the European Extremely Large Telescope (E-ELT). Because of the rotation of the Earth, the night sky is seen as it rotates around the southern celestial pole. As a result of this movement, the stars describe dotted trails when a series of exposures is combined. The closer we look to the celestial equator — here seen near the left edge of the picture — the straighter the trails appear. On the right of the image is the Differential Image Motion Monitor (DIMM), used to measure the atmospheric seeing.